Dear Maria,

I´m quite a new user of DSSAT and soil is clearly not my specialty. But
while reading the SBuild manual, I came across that you can calculate bulk
density from %Clay, %Silt and %stones (Calculate/Edit soil parameters). It
seems to me that the coarse fraction is considered to calculate bulk
density. Anyway, you can try to calculate bulk density with your own
texture fraction values and see which of your 2 bulk density values is more
similar to the calculated one.
It´s only a suggestion, but It may worth it.
Best Regards,
Raúl Giménez

El 19 de abril de 2012 12:31, Jans Bobert <[log in to unmask]> escribió:

> Dear Maria,
>
> you should use the density including the > 2 mm fraction. This is the
> standard method we use in Germany. If you take a look at the DSSAT
> documentation (in the DSSAT folder), you find a description of the
> method for the determination of the bulk density on page 226 pp. (Volume
> 4):
>
> BULK DENSITY
> Core Method
> A core sampler can be a single cylindrical tube or a tube with several
> cylindrical rings
> of known dimensions. The sampler can be driven mechanically or manually
> into the
> soil either horizontally or vertically. Extruded soil from core sampler
> or soils and
> rings are weighed and oven-dried to constant weight at 105°C. The
> oven-dry weight
> divided by the volume of the core sampler or cylindrical ring is the
> bulk density usually
> expressed in g/cm3. This method should not be used for wet (e.g., aquic,
> histic) or
> dry, sandy soils.
>
> As reference the authors mention -> SCS, USDA. 1984. Soil survey
> laboratory methods and procedures for collecting soil samples. In Soil
> Survey Investigation Report No. 1. U.S. Gov. Print. Office, Washington,
> D.C..
>
> Hope this clarifies.
>
> Jans
>
>
> Am 4/19/2012 4:38 PM, schrieb maria soldevilla:
>
>  Thank you very much for the quick responses.
>>
>> In fact, I took the cilinder samples and measured the dry weight, but I
>> also measured the weight of the coarse fraction so I can subtract it from
>> the total and and get the density (without stones) dividing by the volume
>> of the cylinder, as it is common to give the density on that way. My
>> question was which of the two densities should I introduce in the soil
>> file, but I guess it is the total one (including stones).
>>
>> Thank you again
>> Maria
>>
>> 2012/4/19 Jorge Batlle<[log in to unmask]>
>>
>>  Soil bulk density is measured in undisturbed soil samples (ussually token
>>> by
>>> insertion of a cilinder of knwon volume, and dividing the dry weight of
>>> this
>>> soil content by the volume of the cylinder). This measurement can be
>>> related to
>>> total volume porosity if the real density of soil particles is measured
>>> also by
>>> picnometer method.
>>> If you separed coarse fragments>2 mm and fine fraction<  2 mmm, it means
>>> that
>>> you already disturbed your sample.
>>> I hope this help.
>>> Jorge Batlle
>>>
>>>  The bulk density of a soil, is the ratio between the mass and volume of
>>>> a
>>>>
>>> fraction of soil, the most important is that the volume fraction have
>>> included
>>> soil air. This is very important because in the porous part is where
>>> there
>>> is
>>> water movement and more movement of the roots becoming root penetration,
>>> among
>>> other things, like the movement of nutrients or nutrient uptake by the
>>> roots.
>>>
>>>> -----Mensaje original-----
>>>> De: DSSAT - Crop Models and Applications [mailto:[log in to unmask]
>>>> **]
>>>>
>>> En
>>> nombre de fyy0201
>>>
>>>> Enviado el: Jueves, 19 de Abril de 2012 08:15 a.m.
>>>> Para: [log in to unmask]
>>>> Asunto: 回复: Bulk density
>>>>
>>>> Dear colleage,
>>>> I am not familiar with the content mentioned by you.So I am sorry and
>>>>
>>> can not
>>> help you.
>>>
>>>> Best regards,
>>>> Lily
>>>> 2012-04-19
>>>>
>>>>
>>>>
>>>> fyy0201
>>>>
>>>>
>>>>
>>>> 发件人：maria soldevilla
>>>> 发送时间：2012-04-19 21:10
>>>> 主题：Bulk density
>>>> 收件人："DSSAT"<[log in to unmask]**UGA.EDU <[log in to unmask]>>
>>>> æ �送：
>>>>
>>>> Dear colleages.
>>>>
>>>> I have a question and may be somebody can help me. The Bulk density
>>>>
>>> coefficient ( SBDM ) in the soil file, is the soil density including
>>> coarse
>>> elements or without them? I'm not sure which density I should write.
>>>
>>>> Thank you very much
>>>> Best regards
>>>> Maria
>>>>
>>>>
>>>>
>
> --
> ____________________________
>
> Jans Bobert
> Stavangerstrasse 23
> 10439 Berlin
> Germany
> phone: ++49 (0)30 6923768
> email: [log in to unmask]
>